The long-term goal of this project is to develop a magnetic resonance microscope (MRM) suitable for providing sufficiently rapid assessment of tissue pathology to guide surgery. Conventional optical staining, although very effective in diagnosis, is an overnight procedure and for this reason is of limited value in an operating-room (OR) environment. The system uses thin-film transmit/receive coils of YBCO (Y1Ba2Cu3O7), a high-temperature superconductor (HTS). The YBCO coil will provide an improvement in signal-to-noise ratio (SNR) of a factor r10 compared to conventional copper coils. This SNR gain can be used to obtain greater spatial resolution or, alternatively, to reduce the time needed to acquire an image by a factor r100. Consequently, pathology assessments that at present take 24-36 hours can be performed in less than 30 minutes, making MRM a clinically viable tool. The program will have three distinct elements: (1) development of an MRM using a Helmholtz pair for good RF homogeneity at 9.4 T; (2) development of an MRM at 2.0 T for the study of larger specimens at lower resolution; and (3) expansion of the knowledge base of NMR contrast mechanisms and their clinical value in histology. The first part of the effort, proposed here, will address the design of the two microscopes and the construction of a prototype of the 9.4-T machine. In addition, we will design experiments to measure the intrinsic contrast-producing parameters of tissue at the two different fields and make initial designs of pulse sequences to optimize contrast. A follow-on effort will focus on the construction of the 2.0-T system and a demonstration with both systems of the production of images with clinically useful contrast.